System and method for generating electric energy

ABSTRACT

An object of the present invention is to provide a method and a system for implementing the method so as to alleviate the disadvantages of a reciprocating combustion engine and gas turbine in electric energy production. The invention is based on the idea of arranging a combustion chamber ( 10 ) outside a turbine ( 22 ) and providing compressed air from serially connected compressors to the combustion chamber in order to carry out a combustion process supplemented with high pressure steam pulses. The combustion chamber ( 10 ) is arranged to receive compressed air from each compressing stage of the serially connected compressors ( 24 ) for gradually increasing the amount of compressed air in the combustion chamber ( 10 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national stage application filed under 35 USC 371 based onInternational Application No. PCT/FI2015/050346 filed May 20, 2015 andclaims priority under 35 USC 119 of Finnish Patent Application No.20145458 filed May 21, 2014.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC OR ASA TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM (EFS-WEB)

Not Applicable.

STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINTINVENTOR

Not Applicable.

FIELD OF THE INVENTION

The present invention relates to a method of generating electricity andto electric generator system.

BACKGROUND OF THE INVENTION

A typical electric generator system of the prior art consists of acombustion engine, a fuel tank and a generator The combustion enginecomprises a set of cylinders with a corresponding set of reciprocatingpistons. One of the problems associated with the above arrangement isthat the moving pistons and other moving parts have to be constantlylubricated with oil which has a significant impact on runningtemperature of the combustion engine. Consecutively, the runningtemperature is a significant factor when considering the coefficient ofefficiency. The above mentioned engine withstands running temperature ofless than 100 degrees Celsius without a significant deterioration ofdurability. The temperature is too low for vaporizing water andtherefore it cannot be efficiently used for generating electricity i.e.it is just waste heat.

U.S. Pat. No. 2,095,984 (H. Holzwarth) discloses an explosion turbineplant. The explosion turbine plant comprises an impulse rotor,pistonless explosion chambers for generating explosion gases and nozzlesfor expanding and directing the gases to a rotor being drivenexclusively by intermittent puffs of said gases.

Another typical generator system of the prior art consists of a gasturbine and a generator driven by a shaft of the gas turbine. Theproblem with gas turbines is that the combustor is in relatively lowpressure because the gas turbine's combustor is practically an openspace. The low pressure of the combustor significantly drops thecoefficient of efficiency. In Holzwarth turbine plant the intermittentlow pressure significantly drops the coefficient of efficiency.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a method and asystem for implementing the method so as to alleviate the abovedisadvantages.

The invention is based on the idea of arranging a combustion chamberoutside a gas turbine and providing compressed air to the combustionchamber in order to carry out a combustion process in controlled andoptimal conditions and use residue heat from the process. Controllableinput valves are arranged to control the periodic combustion process tomatch a frequency of specific gas oscillations so that these amplifyeach other.

An advantage of the method and system of the invention is that theconditions in the combustion chamber may be optimized for the combustionprocess which significantly increases overall efficiency of the system.The combustion chamber may have running temperature of hundreds ofdegrees Celsius and the pressure inside the compression chamber may besimilar to the pressure in the end of compression stroke in a dieselcycle of a reciprocating combustion engines. Such a temperatureincreases the efficiency of the combustion process and the heat may beeasily converted to electricity due to the high temperature.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of preferred embodiments with reference to the attached drawings,in which

FIG. 1 illustrates a first electric generator system according to anembodiment of the invention;

FIG. 2 illustrates a second electric generator system with steamcirculation system according to an embodiment of the invention;

FIG. 3 illustrates a third electric generator system with an injector orejector system according to an embodiment of the invention;

FIG. 4 illustrates a detail of a system having two combustion chambers;and

FIG. 5 illustrates the changes in pressure over time in a systemaccording to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to a simple example of FIG. 1, the electric generator systemcomprises a turbine 22 which is connection with a generator 26 and acompressor 24 axially or via a transmission 20. The generator may alsobe axially connected to the turbine 22. A rotor of the turbine 22rotates when energy is fed to the turbine by means of fluid flowingthrough the turbine. Rotation of the turbine rotor drives thetransmission 20 and the generator 26 and the compressor 24 which bothare connected to the transmission. The turbine, the generator and thecompressor may be connected to the transmission by means of driveshafts, axles or other suitable power transmission means. Thearrangement converts the energy fed to the turbine 22 into electricenergy output 99 with the generator 26 and into air pressure with thecompressor 24 which compresses air for the combustion chamber 10. In anembodiment the compressor 24 accumulates compressed air into an air tank32 which then feeds the combustion chamber 10 with the compressed airaccumulated in the air tank 32. The compressor 24 is preferably a screwcompressor which is highly efficient and able to provide high pressureto the combustion chamber 10 and to the air tank 32. In an embodiment,the system comprises a second screw compressor connected in series withthe first screw compressor 24 to provide even higher pressure to the airtank. In an embodiment, the system comprises a combination of an axialcompressor 24, such as a radial compressor and a screw compressorconnected in series with the axial compressor 24 to provide air to theair tank. One or more or all of the compressors can be for exampleaxial, radial, screw, piston or some other type of compressor. Theseries of compressors can be a combination of one or more of saidcompressor types connected in parallel or in series. The compressor orthe compressors are preferably arranged to build up pressure of over 20bars to the air tank. In an embodiment, the compressor or thecompressors are arranged to build up pressure of over 30 bars, 35 barsor 40 bars to the air tank. In an embodiment the compressor 24 may bedriven with an electric motor. In an embodiment an intercooler can beprovided between the series-connected first compressor and the secondcompressor to cool down the air between the compressors. In anembodiment intercoolers can be provided between some or all of theseries-connected compressor stages to cool down the air between thecompressors. The intercooler can then be used to generate steam whichcan be injected into the combustion chamber in a form of short, highpressure steam pulses between expansion phases of the combustion cycle.Preferably the combustion inside the combustion chamber is deflagrationcombustion, not detonation combustion.

The electric generator system also comprises a combustion chamber 10which is arranged to receive compressed air from the compressor 24 orfrom the air tank 32 and fuel from a fuel tank 30 to initiate acombustion process. The compressed air is released from the air tankinto the combustion chamber 10 by means of a controllable valve. Thecompressed air is preheated before entering the combustion chamber witha heat recovery unit 40 which conveys heat from the combustion chamberto the compressed air. A regenerator can be used after the lastcompressor to heat up the compressed air before it is fed to thecombustion chamber or to a by-pass duct which bypasses the combustionchamber. The regenerator may use waste heat from e.g. exhaust gas orcombustion chamber for heating up the compressed air. The compressed airmay also be preheated with other means, for example electrically with aresistor, when the system is started and the combustion chamber is atroom temperature. Fuel is released or pumped from the fuel tank andinjected into the combustion chamber. The fuel is preferably diesel orliquid natural gas (LNG). In an embodiment, the fuel is gasoline,natural gas, ethanol, biodiesel or a mixture of two or more thepreceding fuels. In an embodiment, the fuel comprises hydrogen andcarbon monoxide mixture which is a by-product of a soda recovery unit.In an embodiment water or steam may be injected with fuel into thecombustion chamber. In an embodiment the fuel comprises coal dust orbrown coal dust as such or mixed to natural gas, diesel or some othersuitable fuel.

The fuel injected into the combustion chamber ignites due to highpressure and temperature inside the combustion chamber. The highpressure in the combustion chamber is arranged by releasing air from theair tank to the combustion chamber. In addition to the preheating, theheat of the combustion chamber heats up the released air inside thecombustion chamber and builds up even higher pressure. The ignition maybe triggered with an ignition coil, a glow plug, a pre-glow arrangementor a heater arrangement when the system is started and the combustionchamber has not yet reached its running temperature. In an embodimentthe system comprises an antechamber or a pre-combustion chamber. A fuelmixture can be ignited in the pre-combustion chamber to initiate thecombustion process. The combustion process produces heat which heats upthe combustion chamber and keeps the combustion process running byheating the fuel and the compressed air which are introduced into thecombustion chamber. In an embodiment the ignition is also used duringthe combustion cycle after the system is started. In an embodiment theheat recovery unit 40 or other means of heat extraction is used toconvey heat from the combustion chamber or combustion process to wateror steam and generate high pressure steam. The high pressure steam isinjected into the combustion chamber between the expansion phases of thecombustion process. The steam is injected in short, high pressure pulsesand the amount of pulses between two expansion phases may be for example1 to 10, 2 to 8, 3 to 6 or some other amount, such as 4, 5, 7 or 8.

In an embodiment the system comprises means, such as heat exchangers,for producing heat to a district heating system. Some of the thermalenergy that the electric generator system produces can be extracted fromthe system and transferred with heat exchanger to heating water of adistrict heating system. This combined production of electrical andthermal energy raises the overall efficiency of the system.

In an embodiment the system comprises means, such as heat exchangers,for using the thermal energy of the electric generator system to run aabsorption cooling system. Some of the thermal energy that the electricgenerator system produces can be extracted from the system andtransferred with heat exchanger to absorption cooling system which inareas of warm climate may raise the overall efficiency of the system.

The combustion chamber 10 is preferably a hollow container with inputmeans for fuel and compressed air and an output for combustion productsi.e. exhaust gas. The inputs and the output are controllable and may beclosed and opened in specific phases of a combustion cycle in order tobuild up pressure into the combustion chamber before the ignition of thefuel and to expel combustion products after the ignition. Input andoutput can be understood as an inlet and an outlet, respectively, butthe terms input and output are used throughout this text. One or morevalves can be used to control flow to and from the combustion chamber.In an embodiment one or more of the input and/or output valves are socalled radial valves i.e. located radially around the combustion chambercover. The input valves can be fixed to an inclined position to thecombustion chamber i.e. not perpendicular to the combustion chamberwall. The inclined position of a valve produces a whirl of gas in thecombustion chamber when the gas is injected through the inclined valve.This type of whirl can be controlled with the inclined valves whereasrandom whirls produced by perpendicularly positioned valves are verydifficult if not impossible to control. The input valves can be used tocontrol the whirl by selecting suitable inclination angles and/or bytiming openings of the valves. The combustion process in the combustionchamber is a cycle process which at least resembles Diesel cycle.Preheated compressed air from the air tank is introduced into thecombustion chamber and fuel is injected into the combustion chamberuntil the air-fuel mixture ignites. The combustion of the air-fuelmixture expands its volume so the combustion products and the compressedair are expelled through the output when output valve is opened. Runningspeed of the combustion cycle is controlled by controlling the input andoutput valves. The running speed may be chosen freely within certainlimits which are defined by the properties of the system. Suchproperties that may limit the running speed may be for example operationspeed of the valves, the air pressure in the air tank, fuel type, etc.However, the running speed may be adjusted for optimal performance ineach system because it is not restricted by moving pistons or similarphysical limitations of moving mass.

The combustion chamber has preferably a simple form, most preferably asphere or a cylinder, for enabling a quick, clean and completecombustion process. The simple form enables higher running temperatureswhich increases efficiency and decreases the amount of harmful particlesand gases produced during the combustion process. The combustion chamberis arranged to function in high temperatures. In addition to the simpleform, also the material of the combustion chamber has to withstand hightemperatures without significant deterioration of performance ordurability. The material of the combustion chamber may be ceramic,metal, alloy or preferably a combination of two or more materials. Forexample, the combustion chamber may comprise an alloy encasing with aceramic inner coating. The alloy encasing withstands high pressure andstrong forces while the ceramic inner coating withstands high surfacetemperatures. The construction of the combustion chamber is preferablyarranged to withstand running temperature of 400 degrees of Celsius. Inan embodiment the combustion chamber is arranged to withstand runningtemperature of 500, 600, 700 or 800 degrees of Celsius. The combustionchamber itself does not comprise any moving parts so it is relativelysimple task to design the combustion chamber to withstand hightemperatures. The moving parts that experience the highest thermalstress are the valves at the input and output ports of the combustionchamber. However, there are valves readily available that are designedto operate in these temperatures and therefore it should be relativelyeasy task to design and realize a durable valve system.

The output of the combustion chamber 10 leads a stream consisting of thecombustion products and the compressed air from the combustion chamberinto the turbine 22. Due to the high pressure in the combustion chamber,the stream is expelled with high velocity when the output is opened. Theexpelling of the combustion products may be enhanced by having theoutput and the air input open simultaneously for a certain period oftime. The turbine 22 comprises a rotor which rotates when the streamflows through the turbine. The rotating rotor drives the transmission 20which in turn drives the generator 26 and the compressor 24 as statedearlier. The stream is guided to exhaust pipe 90 after the turbine andthe exhaust gas 98 is released from the system.

The combustion chamber 10 is preferably a separate unit outside theturbine 22. The combustion products expelled from the combustion chamber10 are guided to the turbine 22 with a pipe, tube or some other channelconnecting the combustion chamber 10 and the turbine 22. In anembodiment the system comprises multiple combustion chambers. In thatcase each combustion chamber has a pipe, tube or some other channelconnecting that combustion chamber to the turbine 22. Preferably themultiple combustion chambers are arranged to expel their combustionproducts sequentially, i.e. not all at the same time, to provide asteadier flow of combustion products to the turbine 22. In anembodiment, the steadier flow to turbine 22 is accomplished with short,high pressure steam pulses which are injected into the combustionchamber between the expansion phases of the combustion process.

In an embodiment the generator 26 feeds an electric storage system whichcomprises one or more capacitors, super capacitors or batteries forstoring the electrical energy produced by the generator. This type ofsystem can be used in vehicular applications for producing and storingelectrical energy for electrical motors of a vehicle.

Now referring to FIG. 2, in an embodiment the electric generator systemfurther comprises a steam circulation system. The steam circulationsystem comprises a steam tank 34, a heat recovery unit 40, a heatexchanger 42, a condenser 50 and a water tank 36. In an embodiment, thesteam circulation system further comprises a second turbine. Water andsteam circulates in the steam circulation system wherein the water isaccumulated into the water tank 36 and the steam is accumulated into thesteam tank 34. In an embodiment the steam tank and the water tank is asingle tank wherein the water is accumulated in the bottom of the tankand steam is accumulated on the top of the tank. The flowing of thesteam is based on pressure differences within the system but it might beassisted with pumps or similar arrangement if necessary. The flowing iscontrolled by means of a number of valves which may be operated incontrolled manner.

The steam is arranged to flow from the steam tank 34 to the heatrecovery unit 40. The heat recovery unit 40 is in thermal connectionwith the combustion chamber 10 so that the combustion chamber heats upthe heat recovery unit in which the heat is conveyed to the steamflowing through the heat recovery unit. The heat recovery unit may be aseparate unit having a thermal connection to the combustion chamber orit may be a fixed part of the combustion chamber. In an embodiment theheat recovery unit may even a pipework inside the combustion chamber ortubing on the surface of the combustion chamber. When the heat from thecombustion chamber is conveyed to the steam flowing through the heatrecovery unit, the steam rapidly heats up and expands. The steam flow isthen directed to the turbine 22 wherein the steam flow rotates the rotorof the turbine 22 simultaneously with the combustion products andcompressed air which are expelled from the combustion chamber 10 intothe turbine 22.

In an embodiment a heat pump can be used to produce steam. Heat pumpsare known to be effective when needed temperature difference is small. Aheat pump is therefore a good alternative for adding thermal energy towater which is at or near its boiling point. For example an air-to-wateror water-to-water heat pump can be used for producing steam from waterthat is preheated to near or at its boiling point. The steam productioncan be assisted with other energy sources, including those alreadymentioned, in addition to the heat pump. In an embodiment steam ofexhaust flow is condensed into water and the heat released from thecondensing is used as a heat source for the heat pump. The temperaturewhere the condensing takes place depends on the pressure of the exhaustgas and steam. Said temperature is 100 degrees Celsius in atmosphericpressure but in higher pressure it can be for example as high as 200,300, 400 or even 500 degrees Celsius. The heat pump uses the heat tovaporize water for providing fresh steam to the system. In an embodimentheat provided by one or more intercoolers of the system is used as aheat source for the heat pump.

In an embodiment the heat recovery unit 40 is replaced with heatinsulating material and time-dependent steam injections to thecombustion chamber 10 maintain a stable running temperature of thecombustion chamber. The time-dependent steam injections are preferablyshort, high pressure steam pulses injected into the combustion chamberbetween expansion phases of the combustion process. The injected highpressure steam pulses need only a reduced amount of steam due to theirshort pulse type length. After injection the steam exits the combustionchamber and enters into the turbine 22.

In an embodiment the system comprises an additional burner forincreasing the amount and/or the temperature of the steam in the system.The burner preferably uses the same type of fuel as the rest of thesystem. The fuel is burned in the burner for producing heat which thenheats steam and/or the burning fuel heats water to produce steam. Theadditional burner can be used in systems which do not produce enough“waste heat” to produce an adequate amount of steam. The use of theadditional burner ensures that a desired amount of steam in a desiredtemperature and pressure can be achieved.

In an embodiment, the steam is not directed into the same turbine 22 asthe combustion products. In that embodiment the system comprises asecond turbine which is dedicated to the steam stream while the (first)turbine 22 is dedicated to the stream of combustion products andcompressed air. The stream of combustion products and compressed air mayeven be arranged to flow through an additional heat exchanger after theturbine 22 to heat up the steam stream before that stream enters thesecond turbine. The arrangement of the second turbine may be similar toknown combined cycle power plants.

From the turbine a stream of steam, compressed air and combustionproducts flows through the heat exchanger 42 to the condenser 50 whereinthe steam is condensed into water and the compressed air and thecombustion products are guided out of the system through exhaust pipe90. In the embodiment of the second turbine the stream of combustionproducts and compressed air is arranged to flow through heat exchanger42 directly to exhaust pipe and the steam stream is arranged to flowthrough the heat exchanger 42 and the condenser 50 to the water tank 36.

Condensing water from the exhaust flow may cause accumulation ofimpurities to the system which is undesirable. In an embodiment this issolved by feeding the condenser with fresh, atmospheric air from whichrelatively clean water can be condensed to the system.

The water condensed from the steam and/or from the atmospheric air flowsinto the water tank 36 or is pumped in there. An ion exchanger 52 may bearranged between the condenser 50 and the water tank 36 for purifyingthe water before it enters the cycle again. The water tank 36accumulates water which is then guided or pumped to the heat exchanger42. The heat exchanger conveys the heat from the stream of steam,compressed air and combustion products to the water flowing through theheat exchanger. The heat of the heat exchanger vaporizes the water intosteam which is then guided to flow back into the steam tank 34. From thesteam tank 34 the high pressure steam can be released in short bursts tocreate short, high pressure pulses to the combustion chamber.

FIG. 3 illustrates an electric generator system which is otherwisesimilar to the system of FIG. 2 except that the system further comprisesa pump having a converging-diverging nozzle, for example an injector orejector 12 for combining the stream of combustion products from thecombustion chamber 10 and the steam from the heat recovery unit 40 orfrom the heat exchanger 42 wherein the ejector 12 guides the steam andcombustion products into the turbine 22 for rotating the rotor of theturbine. The pump having a converging-diverging nozzle is called anejector within the description but in an embodiment the pump can also befor example an injector, steam injector or steam ejector. The ejector 12is between the turbine and the combustion chamber and its heat recoveryunit. The combustion products and the compressed air are expelled intothe ejector wherein the steam from the heat recovery unit is superheatedby the hot matter from the combustion chamber. The superheating of thesteam causes rapid expansion of the steam. The ejector 12 guides thestream of superheated steam, combustion products and compressed air intothe turbine 22 wherein the stream rotates the rotor of the turbine. Inan embodiment, short, high pressure steam pulses are injected into theejector 12 from where the steam flows to the turbine and rotates therotor or the turbine. In an embodiment an afterburner can be used in theejector 12 between the combustion chamber 10 and the turbine 22.However, the temperature of the exhaust gas has to be monitored andcontrolled since the input gas of the turbine should preferably have alow temperature and the afterburner rises the temperature of the exhaustgas. In an embodiment the afterburner is used intermittently and notcontinuously.

In an embodiment the system also comprises an adjustable nozzle and avalve in connection with the ejector 12 and the output of the combustionchamber 10 for adjusting the expelling of combustion products from thecombustion chamber 10. The nozzle has a certain design and a form whichmay be altered. The nozzle is within the ejector in a by-pass flow ofthe steam flowing from the heat recovery unit 40 to the turbine 22. Theform of the nozzle has a significant impact to the expelling of thecombustion products from the combustion chamber when the valve in theoutput is open. By altering the form of the nozzle the expelling of thecombustion products may be increased with help of the by-pass flow ofthe steam.

In an embodiment a portion of the combustion products, i.e. the exhaustgas, is guided to a low temperature/pressure region of the turbine 22 orto a low pressure turbine when the exhaust gas is exhaust from thecombustion chamber. An ejector or ejectors (14 a, 14 b) can be omittedin this embodiment since the pressure in suction side is higher than thepressure in low temperature/pressure region.

FIG. 4 illustrates a detail of an embodiment of a combustion systemhaving two combustion chambers 10 a and 10 b and an ejector 12. Thenumber of combustion chambers and ejectors is not limited to thisexample. Two combustion chambers and one ejector were chosen for thisembodiment to give an example and represent the capabilities of thesystem. In an embodiment the electric combustion system has one, two,three, four or more combustion chambers and zero, one, two, three, fouror more ejectors. In an embodiment the ejectors are not essential andthe system can operate without a single ejector.

Each combustion chamber 10 a, 10 b comprises one or more inputs 101, 102which can be controlled with or without input valves and one or moreoutputs 111, 112 which can be open or controlled with output valves. Theinputs and the outputs may be controlled without valves by controllingthe pressure of the inputs and outputs because gases tend to flow from ahigher pressure region to a lower pressure region. In an embodiment atleast some of the inputs and outputs are controlled with gas vibrationsor oscillations instead of valves. Movement of gas in a pipeline tendsto oscillate with a frequency or a plurality of frequencies which is/arespecific to the pipeline and the gas, so called eigenfrequencies. Thepulse action is created by the periodic combustion and fortified by theeigenfrequencies of the flow system. Specific oscillation frequenciescan be exploited by controlling the periodic combustion process to matchthe frequency of the specific gas oscillation so that these amplify eachother. In an embodiment the combustion cycle is matched with thespecific oscillation frequency of the compressed air flowing in thesystem. In an embodiment valve actuation is optimized to harmonize withthe desired periodical operation of the pulse turbine. In an embodimentthe combustion cycle, the specific oscillation frequency of thecompressed air flowing in the system and a specific oscillationfrequency of the steam flowing in the system are all matched to the samephase so that they amplify each other. The specific oscillationfrequencies of the steam and the compressed air flows can be matchedwith pipeline design. In an embodiment the combustion cycle is matchedwith the specific oscillation frequency of the compressed air flowing inthe system and with the specific oscillation frequency of the steamflowing in the system but the specific frequencies of the steam and thecompressed air are not matched with each other. Preferably the flowsystem is optimized such that the flow losses are minimized.

In an embodiment the system comprises compressors connected in series toproduce high pressure compressed air to the combustion chamber. Atypical way is to feed compressed air from the first compressor to thesecond compressor and from the second compressor to the thirdcompressor, and so on. The pressure of the compressed air builds up ineach compressor stage and finally the compressed air from the lastcompressor of the series of compressors is released to the combustionchamber. This is energy consuming as the amount (mass) of compressed airis the same in each compressing stage. A compressing stage can be asingle compressor or a number of compressors in parallel connection i.e.each having common input and output. In an embodiment a portion of themass of the compressed air is released to the combustion chamber and theremaining portion of the mass of the compressed air is released to thefollowing compressor in the series of compressors. The pressure withinthe combustion chamber rises gradually as the compressed air is releasedto the combustion chamber between compressing stages. Heat can beextracted from the compressed air between the compressing stages byusing one or more intercoolers. Also the amount of air to be compresseddiminishes in subsequent compressing stages as part of the air isreleased to the combustion chamber between the compressing stages. Aplurality of pressure tanks can be used for storing compressed air invarious pressures between atmospheric pressure and the highest pressurefrom the last compressor. A further advantage is that the gradual airfeeding allows the other inputs to be fed to the combustion chamberduring a desired pressure. For example the combustion chamber couldfirst receive a first release of compressed air, then a fuel input, thena second release of compressed air, then a steam input and finally athird release of compressed air to a desired final pressure. The orderand timing of the inputs can be optimized based on the system variables.

In an embodiment each combustion chamber comprises an output controlledby a main exhaust valve 111. In an embodiment each combustion chambercomprises two outputs, one output being controlled by a main exhaustvalve 111 and one output being controlled by an auxiliary exhaust valve112. In an embodiment each combustion chamber comprises an open outputwhich is not controlled by valve. In an embodiment each combustionchamber comprises an input 101 for fuel. In an embodiment eachcombustion chamber comprises inputs 101, 102 for fuel and pressurizedair. In an embodiment each combustion chamber comprises inputs for fuel,pressurized air and steam. In an embodiment each combustion chambercomprises inputs for one or more of the following: fuel, pressurizedair, steam and water. The steam may be produced at least partially usingwaste heat of the combustion process of the system. In an embodiment,the steam is injected in the form of short, high pressure steam pulseswhich are injected into the combustion chamber between the expansionphases of the combustion process. In this embodiment, the exhaust valvesmay be omitted as the pressure and temperature conditions of thecombustion chamber are controlled with the steam pulse injections. In anembodiment steam is injected into combustion chamber and/or to theejector 12 and to the turbine 22. When both combustion chambers outputsare closed, steam can be injected directly into the ejector 12. In anembodiment, an ORC turbine or a Stirling engine can be used after theheat exchanger for cooling the exhaust gas and steam in a temperaturerange of about 200 degrees Celsius.

A combustion cycle in the system of FIG. 4 could have the followingsteps. First pressurized air is fed to the combustion chambers 10 a, 10b via air inputs 102 and fuel is fed to the combustion chambers 10 a, 10b via fuel inputs 101. In an embodiment fuels, especially gaseous fuels,can be compressed prior to feeding them into the combustion chamber.Fuels like for example carbon monoxide or hydrogen can be fed in apressure higher than atmospheric pressure to the combustion chamber. Thepressure in the combustion chambers is built up due to residue heatuntil the fuel in the combustion chambers ignites, for example at 20 to30 bar pressure, and produces combustion products and more pressure. Thecombustion products and the pressure are released to the ejector 12 byopening the main exhaust valve 111 between a combustion chamber 10 a andthe ejector 12. In an embodiment the main exhaust valve is omitted andthe combustion products move freely to the ejector 12. In an embodimenta pressure wave supercharger replaces the main exhaust valve. Preferablythe combustion cycles in each combustion chamber runs with a phasedifference to the other combustion chambers so that the exhaust streamfrom the combustion chambers is steadier and less pulse-like. Thecombustion products flow from the combustion chamber to the ejector 12and from ejector to turbine 22 through an output 113. At the same time,liquid water and/or water vapour i.e. steam can be injected to thecombustion chamber 10 a via inputs and thus improving the ventilation ofthe combustion products out of the combustion chamber. Preferably steamis injected into the combustion chamber in short pulses with high steampressure, for example ranging from tens of bars to hundred bars. Theinjection of steam also helps to keep the pressure in an elevated levelfor an extended period of time as can be seen from FIG. 5. The injectionof water and/or steam also lowers the temperature of the combustionchamber and facilitates temperature controlling. The combustion chambermay have ducts formed within combustion chamber cover for water and/orsteam circulation on exhaust side of the combustion chamber. The waterand/or steam can be injected into the ducts which water and/or steamthen perspirates from small apertures of the ducts. Heat is transferredfrom the exhaust side of the combustion chamber to the perspiratinginjected water and/or steam and the combustion chamber cools down. In anembodiment similar ducts and cooling system is used on the main exhaustvalve. The injection lowers the temperature of the main exhaust valve111 which can extend the lifetime of the main exhaust valve 111. Whenthe pressure in the combustion chamber and in the ejector has dropped,for example to 40 to 50 bars, the main exhaust valve 111 is closed. Oneor more of the valves may be electronically controlled for example via acontrol unit. In an embodiment the main exhaust valve 111 can be omittedwhen steam pulses are injected into the combustion chamber so the mainexhaust output is constantly open.

In an embodiment including the main exhaust valve, after closing themain exhaust valve 111 the ejector can be sprayed with liquid waterand/or water vapour i.e. steam via valve 103 which raise the pressure inthe ejector 12, for example to 65 bars. At a certain pressure in theejector 12, for example 65 bars, the main exhaust valve 111 of thesecond combustion chamber 10 b opens and releases combustion products tothe ejector 12 and from there to the turbine 22. At the same time thesecondary exhaust valve 112 of the first combustion chamber 10 a is keptopen to ventilate the residue combustion products from the firstcombustion chamber 10 a. The ventilation can be enhanced by introducingpressurized air or steam via the inputs 101, 102 to the combustionchamber. The secondary exhaust valve 112 may lead the residue combustionproducts to the turbine 22 via one or more second ejectors 14 a, 14 b.In an embodiment steam is injected into combustion chamber and/or to theejector 12 and to the turbine 22. When both combustion chambers outputsare closed, steam can be injected directly into the ejector 12. In anembodiment a single second ejector can comprise multiple inputs so thatit can be used with two combustion chambers. Once the first combustionchamber 10 a is ventilated and the pressure has dropped to asufficiently low level, for example to 20, 10, 5 or 2 bars, thesecondary exhaust valve 112 is closed and the next cycle of thecombustion cycle can begin.

In an embodiment the second ejector 14 a, 14 b is arranged to receivemotive steam or motive gas via input 114. The motive gas is preferablypressurized water vapour for example in 60, 80 or 100 bar pressure. Themotive gas is directed through the second ejector 14 a, 14 b anddischarged to the ejector 12 via valve 104. When the motive gas goesthrough the second ejector it creates a suction effect drawing residuecombustion products from a combustion chamber 10 a, 10 b when outputvalve 112 connecting the combustion chamber to the second ejector isopen. The valve 104 is preferably a control valve. The throughput and/oropening direction of the valve 104 can be adjusted. In an embodiment allexcess steam produced within the system can be fed to the turbine viathe valve 104 and/or the second ejector 14 a, 14 b.

In an embodiment a back flow from the turbine 22 using an intermediatesteam tapping can be introduced to a third ejector. The back flow or theintermediate steam from the turbine may comprise steam or combustionproducts or a mixture of steam and combustion products which areintroduce to the third ejector. The pressure of the intermediate steamat the third ejector is raised to a sufficient level by using valves andintroducing gas such as water vapour to the third ejector. The steam andthe combustion products increase the volume of the gas and decrease thetemperature of the gas. The mixture of gases is introduced from thethird ejector to the ejector 12 for example via the second ejector 14 a,14 b and valve 104, or to some other input valve of the system. In anembodiment, an output using an intermediate steam tapping can also beintroduced right after the heat exchanger.

In an embodiment the turbine is arranged to rotate a by-pass fan in anaviation application for example replacing turbofan engines ofcommercial airplanes. In an embodiment the system comprises an oxygentank connected to the combustion chamber and controlled with a valve.The combustion chamber can be used as a combustion chamber of rocketengine using rocket fuel from the fuel tank and oxygen from theatmosphere in the lower atmosphere so that the oxygen from the oxygentank can be used in the upper atmosphere where the amount of oxygen isnot sufficient for the combustion.

FIG. 5 illustrates time dependence of pressure in a system according toan embodiment. As the combustion cycle causes the pressure to changewithin the system in rather broad range, the turbine 22 does not receiveoptimal input unless the system in controlled in a time-dependentmanner. Preferably all the inputs 101, 102, 103, 104 are controlled intime-dependent manner to keep the output 113 to the turbine in optimalpressure. Without any other time-dependent inputs than fuel and air, theoutput to the turbine would look like the curve 200 in FIG. 5. In thebeginning of the combustion cycle the pressure builds up quickly peakingjust before the main exhaust valve 111 is opened which quickly lowersthe pressure as the combustion products flow through the turbine. Now ifthe combustion chamber is injected with liquid water and/or water vapourimmediately after the main exhaust valve 111 is opened, the pressurewould not fall as quickly because the liquid water would evaporate andthe vapour would heat up due to residue heat of the combustion chamberand thus the injection would lessen the impact of opening the mainexhaust valve 111. In a similar manner, once the main exhaust valve 111has been closed, the ejector can be sprayed with liquid water and/orwater vapour i.e. steam via valve 103 which raise the pressure in theejector 12 thus raising the output pressure to the turbine. The amountof liquid water, steam and air is controlled in a time-dependent mannerin order to prevent the output to the turbine from dropping too much.Keeping the output to the turbine in an elevated and relatively constantlevel has a significant impact on the efficiency of the system. Theturbine can be driven in optimal operating range most of the time with arelatively constant output whereas the turbine can not make the most outof sparse, short bursts.

The output to the turbine can be maintained in an elevated level withthe injection of water, steam and air. This elevated level isillustrated with dashed line 201 in FIG. 5. However, a lot of steam andair is needed to maintain such a high pressure if the main exhaust valveis omitted or kept constantly open. If the injection of steam is in theform of very short and high pressure pulses, the main exhaust valve canbe omitted thus simplifying the system and increasing its reliability.Curve 202 represents the pressure level during a combustion cycle whenthe injections are in the form of short steam pulses. The short steampulses can maintain the average pressure at a high enough level that themain exhaust valve is not necessary. The short steam pulses may havepeak pressure higher than the pressure pulse caused by the combustion.In an embodiment of e.g. two combustion chambers, short steam pulses canbe fed to the system (e.g. to the first combustion chamber) after fuelis ignited and combustion products expelled from the first combustionchamber. The feeding of steam pulses can be continued while an exhaustvalve of the second combustion chamber is closed. During that time anyresidue steam and combustion products are flushed from the secondcombustion chamber. The second combustion chamber is flushed with aninput of compressed air which flows through e.g. a secondary exhaustvalve 112 which then conveys the air and the residues to e.g. lowerpressure turbine. After the flushing the second combustion chamber isfilled with compressed air, fuel is injected to the second combustionchamber and the mixture ignites or is ignited. After the fuel is ignitedand combustion products expelled from the second combustion chamber,short steam pulses can be fed to the system (e.g. to the secondcombustion chamber) while the exhaust valve of the first combustionchamber is closed, the first combustion chamber is flushed, filled andignited like the second combustion chamber earlier, and so on. Thisenables high enough pressure for efficient use of the turbine throughoutthe process.

In an embodiment the pressure within the ejector 12 is kept always overfor example 20, 30, 40 or 50 bars. In an embodiment the amount ofinjected water, steam and air and point of time at which those areinjected are determined based on measured quantities of the system. Suchmeasured quantities can be for example temperature, pressure, humidity,gas composition, state of a valve or some other process quantity. Saidquantities can be measured with e.g. sensors. In an embodiment theamount of injected water, steam and air and point of time at which thoseare injected are determined based on the phase of the combustion cycle.The time dependent injection of water, steam also increases thereliability of the turbine 22 by controlling the temperature of the gaswhich is introduced to the turbine 22. The injection of water and steamlowers the average temperature of the gas introduced to the turbine andtherefore it allows for higher pressure (and thus higher temperature) tobe used in the combustion chamber.

It will be obvious to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The invention and its embodiments are not limited to the examplesdescribed above but may vary within the scope of the claims.

The invention claimed is:
 1. An electric generator system having aturbine in connection with a generator and one or more compressors forconverting energy fed to the turbine into electric energy with thegenerator and to compress air with one or more compressors, a combustionchamber arranged to receive compressed air from the one or morecompressors and fuel from a fuel tank to initiate a combustion processand output combustion products into the turbine for rotating the rotorof the turbine, the combustion process being a cycle process comprisinga compression phase and an expansion phase, the combustion process beinga constant-volume Humphrey cycle process, one or more fuel input valvesfor providing the fuel to the combustion chamber, one or more air inputvalves for providing the compressed air to the combustion chamber, oneor more steam input valves for providing steam to the combustionchamber, a control unit for controlling said one or more fuel inputvalves, said one or more air input valves and said one or more steaminput valves, whereby said one or more fuel input valves and said one ormore air input valves are controlled to match the cyclic combustionprocess to a frequency of specific gas oscillations so that thecombustion process cycle and the specific gas oscillations amplify eachother, said one or more steam input valves are controlled to generate aplurality of time-dependent, short, high-pressure steam injection pulsesinto the combustion chamber within a single combustion cycle betweenexpansion phases of the combustion process.
 2. An electric generatorsystem as claimed in claim 1, wherein the system further comprises: aheat exchanger in thermal interaction with the combustion productsexhaust from the turbine for transferring heat from the exhaustcombustion products into steam.
 3. An electric generator system asclaimed in claim 1, wherein the system further comprises: a steam tankfor accumulating steam, a condenser for condensing the steam into water,a water tank for accumulating the water, and means for pumping the waterfrom the water tank to a heat exchanger for vaporizing the water intosteam which is arranged to flow into the steam tank.
 4. An electricgenerator system as claimed in claim 1, wherein said one or more airinput valves for controlling the combustion process is/are fixed to aninclined position to the normal of the wall of the combustion chamber sothat an input of gas produces a controlled whirl of gas to thecombustion chamber.
 5. An electric generator system as claimed in claim1, wherein the system further comprises an air tank for accumulatingcompressed air from one or more compressors and for providing thecompressed air to the combustion chamber.
 6. An electric generatorsystem as claimed in claim 5, wherein the system comprises an air tankfor accumulating compressed air from each compressing stage of seriallyconnected compressors and for providing the compressed air in variouspressures to the combustion chamber.
 7. An electric generator system asclaimed in claim 1, wherein the fuel used in the system is one of thefollowing group: diesel, gasoline, ethanol, natural gas, liquid naturalgas and mixture of hydrogen and carbon monoxide.
 8. An electricgenerator system as claimed in claim 1, wherein the system comprisesheating means for preheating the compressed air prior to beingintroduced into the combustion chamber.
 9. An electric generator systemas claimed in claim 1, wherein the system comprises a pre-combustionchamber for igniting a fuel mixture in the pre-combustion chamber toinitiate the combustion process.
 10. A method for generating electricenergy comprising: providing an input of fuel to a combustion chamber,providing an input of compressed air to the combustion chamber,providing an input of steam to the combustion chamber, providing astream of combustion products and compressed air from the combustionchamber to a turbine for producing power, operating a generator usingthe power the turbine produces for generating electric energy, operatingone or more compressors for compressing air for the combustion chamber,and controlling the input of fuel and the input of compressed air to thecombustion chamber in order to run a combustion cycle process in thecombustion chamber, the cycle process comprising a compression phase andan expansion phase and the combustion process being a constant-volumeHumphrey cycle process, controlling the input of fuel and the input ofcompressed air to the combustion chamber such that the combustionprocess cycle matches a frequency of specific gas oscillations so thatthe combustion process cycle and the specific gas oscillations amplifyeach other, controlling the input of steam to the combustion chamber sothat the steam is injected in plurality of time-dependent, short,high-pressure pulses within a single combustion cycle between expansionphases of the combustion process.
 11. A method as claimed in claim 10,wherein the method further comprises-extracting heat from the combustionprocess for producing and heating steam.
 12. A method as claimed inclaim 10, wherein the method further comprises a step of controlling anejector input valve for creating steam pulses or water pulses to theejector located between the combustion chamber and the turbine.
 13. Amethod as claimed in claim 10, wherein the method further comprises astep of flushing residue steam and combustion products from thecombustion chamber while a main exhaust valve of the combustion chamberis closed, wherein the combustion chamber is flushed with an input ofcompressed air which flows through a secondary exhaust valve of thecombustion chamber to a lower pressure turbine.